Engine induction systems can produce noise and are therefore sometimes equipped with noise reducers. Such noise reducers can be located upstream of the induction system and allow air to flow through them while reducing noise from the induction system. The noise reduction can be achieved through a variety of means, including specially shaped passages, placement of deflectors in passages through which sound travels, and adding chambers which trap the sound waves to dissipate the noise.
A disadvantage associated with adding chambers is that they can have obstructions which inhibit reflection of the waves entering the chamber off the interior walls of the chamber and out of the chamber. Such reflection can produce destructive interference between the sound waves exiting the chamber and the sound waves in the induction system resulting in substantial noise reduction. A disadvantage associated with specially shaping passages and adding deflectors is that such features can increase the complexity of the noise reducer making fabrication more difficult.
Noise reducers can also include additional components such as sensors and air filters. The addition of such components can reduce the compatibility of the noise reducer with different induction systems since each of the additional components must be suitable for the induction system. Including such additional components also increases the complexity of the noise reducer making fabrication more difficult.